The present invention relates to an apparatus for determining the type and remaining capacity of a tape.
In a recording and reproducing apparatus such as a video tape recorder (VTR), audio tape recorder, or the like, a magnetic tape is used as a signal recording medium. This tape is usually received within a tape cassette and is wound at its ends around a take-up reel hub and a tape supply reel hub, respectively. When the tape cassette is loaded in the recording and reproducing apparatus, it is important for a tape user to have a clear knowledge of the remaining capacity of the tape wound around the tape supply reel.
When the user has no knowledge of the remaining capacity of the tape while the apparatus is in a recording mode, there is a possibility that recording of an important program may be missed due to a shortage of the remaining capacity of the tape, or that uneconomical use of the tape may occur due to excess remaining in the tape.
Also, if the user knows the remaining capacity of the tape, such knowledge is convenient in finding the starting position of a recorded program to use the remaining tape capacity. Since there are more than one types of tape cassettes, if the user knows the type of tape to be used, he can determine the entire recording time of the tape.
U.S. Pat. No. 4,280,159 discloses an example of a device for displaying the remaining capacity of such tape. This device is designed to measure the rotational periods Ts and Tt of a tape-supply reel and a take-up reel and to determine the value of Ts.sup.2 +Tt.sup.2. Then, the device discriminates the type of tape by using the value of Ts.sup.2 +Tt.sup.2 and calculates the remaining tape capacity by using the discriminated character of the tape and the rotational periods Ts and Tt.
However, measurement is made of the rotational periods of the reels based on the speed of tape travel being kept constant. For this reason, when variations occur in the speed of tape during the measurement of the rotational periods of the reels, the measurement will contain errors.